Entering the Freeway.? A car sits on an entrance ramp to a freeway, waiting for a break in the traffic. Then the driver accelerates with constant acceleration along the ramp and onto the freeway. The car starts from rest, moves in a straight line, and has a speed of 20 m/s (45 mi/h) when it reaches the end of the 120-m-long ramp. (a) What is the acceleration of the car? (b) How much time does it take the car to travel the length of the ramp? (c) The traffic on the freeway is moving at a constant speed of 20 m/s. What distance does the traffic travel while the car is moving the length of the ramp?

Solution 28E Step 1: Given data The car initially at rest , u = 0 m/s Speed v = 20 m/s Length of the ramp (s) = 120 m Problem (a) Step 1: To find the acceleration of the car Since the value of time is not given and the speed is not constant We should take the equation of motion 2 2 v = u + 2as u = 0,